Applied Akka Patterns

Preface

Reactive Application Development is the new frontier of software development. As the prevalence of connected devices has increased, so has the amount of data available. Older techniques for processing that data in a single-threaded batch simply can’t hold up under the demands presented by this new world. Big data is on the rise and we need new tools and new techniques to deal with it.

Often, the solution to modern problems doesn’t come from the present, but rather from the past. Many of today’s new tools for processing big data are in fact based on the older concept of actors. Actors are the key concept from which Akka was built, but it has its roots in the past. It isn’t a new concept; rather, it’s an old one brought to light in the modern world.

As we set forth to explore Akka, actors, streams, and all the other things associated with them, we will be approaching them from the perspective of a real-world concern: the problem of how to schedule a group of people across a variety of projects while optimizing both for the time they have available, as well as their skill sets. This is a complex problem, not one easily solved in an afternoon. But it is an interesting issue that provides a lot of room for depth. It is also a problem that most software developers will be involved with at some point during their career. We will refer back to this problem throughout our exploration of Akka.

But before we get to solving the problems of our domain, we have to first understand the tools that we have available. We also need to understand why those tools exist, and what kinds of problems they were intended to solve. We need to know the origin of Akka, with its roots in the Actor Model. We need a guiding set of principles to help us stitch together our application, found in our exploration of domain-driven design (DDD). From there, we can begin to build out our domain, using all of the tools Akka provides. We can explore the use of simple actors and how they relate to streams. We can take our system and distribute across multiple nodes, providing better fault tolerance, availability, and of course, scalability.

But first, we need to know where it all came from.

Conventions Used in This Book

The following typographical conventions are used in this book:

Italic

Indicates new terms, URLs, email addresses, filenames, and file extensions.

Constant width

Used for program listings, as well as within paragraphs to refer to program elements such as variable or function names, databases, data types, environment variables, statements, and keywords.

Constant width bold

Shows commands or other text that should be typed literally by the user.

Constant width italic

Shows text that should be replaced with user-supplied values or by values determined by context.

Tip

This element signifies a tip or suggestion.

Note

This element signifies a general note.

Warning

This element indicates a warning or caution.

O’Reilly Safari

Note

Safari (formerly Safari Books Online) is membership-based training and reference platform for enterprise, government, educators, and individuals.

Members have access to thousands of books, training videos, Learning Paths, interactive tutorials, and curated playlists from over 250 publishers, including O’Reilly Media, Harvard Business Review, Prentice Hall Professional, Addison-Wesley Professional, Microsoft Press, Sams, Que, Peachpit Press, Adobe, Focal Press, Cisco Press, John Wiley & Sons, Syngress, Morgan Kaufmann, IBM Redbooks, Packt, Adobe Press, FT Press, Apress, Manning, New Riders, McGraw-Hill, Jones & Bartlett, and Course Technology, among others.

For more information, please visit http://oreilly.com/safari.

How to Contact Us

Please address comments and questions concerning this book to the publisher:

• O’Reilly Media, Inc.
• 1005 Gravenstein Highway North
• Sebastopol, CA 95472
• 800-998-9938 (in the United States or Canada)
• 707-829-0515 (international or local)
• 707-829-0104 (fax)

We have a web page for this book, where we list errata, examples, and any additional information. You can access this page at http://bit.ly/applied_akka_patterns.

To comment or ask technical questions about this book, send email to [e-mail].

For more information about our books, courses, conferences, and news, see our website at http://www.oreilly.com.

Find us on Facebook: http://facebook.com/oreilly

Follow us on Twitter: http://twitter.com/oreillymedia

Watch us on YouTube: http://www.youtube.com/oreillymedia

Acknowledgments

We would like to thank the many people who helped make this book possible, including the Akka team, both within Lightbend and in the greater community, as well as our editor, Nan Barber, and our reviewers, Konrad Malawski, Sean Glover, and Petro Verkhogliad. We especially want to thank our families for their patience and support.